Bureau of Reclamation: Lower Colorado Region - Colorado River and Hoover Dam Facts and Figures How is the Colorado River Basin divided? The Colorado River Compact divided the Colorado River Basin into the Upper Basin and the Lower Basin. The division point is Lees Ferry, a point in the mainstem of the Colorado River about 30 river miles south of the Utah-Arizona boundary. The "Upper Basin" includes those parts of the States of Arizona, Colorado, New Mexico, Utah, and Wyoming within and from which waters naturally drain into the Colorado River system above Lees Ferry, and all parts of these States that are not part of the river's drainage system but may benefit from water diverted from the system above Lees Ferry. The "Lower Basin" includes those parts of the States of Arizona, California, Nevada, New Mexico, and Utah within and from which waters naturally drain into the Colorado River system below Lees Ferry, and all parts of these States that are not part of the river's drainage system but may benefit from water diverted from the system below Lees Ferry. How is Colorado River water apportioned?

The Colorado River Compact apportioned to each basin the exclusive, beneficial consumptive use of 7,500,000 acre-feet of water per year from the Colorado River system in perpetuity. In addition, the Compact gave to the Lower Basin the right to increase its annual beneficial consumptive use of such water by 1,000,000 acre-feet. How much water is apportioned to each State in the Colorado River Basin? The Colorado River Compact did not apportion water to any State. On October 11, 1948, the Upper Basin States entered into the Upper Colorado River Basin Compact, which apportioned use of the Upper Basin waters among them. The compact permits Arizona to use 50,000 acre-feet of water annually from the upper Colorado River system, and apportioned the remaining water to the Upper Basin States in the following percentages: Colorado, 51.75 percent; New Mexico, 11.25 percent; Utah, 23 percent; and Wyoming, 14 percent. The Lower Basin States of Arizona, California, and Nevada were not able to reach agreement.

In 1952, Arizona filed suit in the United States Supreme Court to determine how the waters of the Lower Basin should be divided. In October 1962, the Court ruled that of the first 7,500,000 acre-feet of mainstem water in the Lower Basin, California is entitled to 4,400,000 acre-feet, Arizona 2,800,000 acre-feet, and Nevada, 300,000 acre-feet. The United States has contracted with the States of Arizona and Nevada and with various agencies in Arizona and California for the delivery of Colorado River water. These contracts make delivery of the water contingent upon its availability for use in the respective States under the Colorado River Compact and the Boulder Canyon Project Act. The United States and Mexico entered into a treaty on February 3, 1944, which guarantees Mexico 1,500,000 acre-feet of Colorado River water annually. This entitlement is subject to increase or decrease under certain circumstances provided for in the treaty. Hoover Dam How much concrete is in the dam? Three and one-quarter million cubic yards.

There are 4,360,000 cubic yards of concrete in the dam, powerplant, and appurtenant works. This much concrete would build a monument 100 feet square and 2-1/2 miles high; would rise higher than the Empire State Building (which is 1,250 feet) if placed on an ordinary city block; or would pave a standard highway, 16 feet wide, from San Francisco to New York City. The first concrete for the dam was placed on June 6, 1933, and the last concrete was placed in the dam on May 29, 1935. Approximately 160,000 cubic yards of concrete were placed in the dam per month. Peak placements were 10,462 cubic yards in one day (including some concrete placed in the intake towers and powerplant), and slightly over 275,000 cubic yards in one month. What was an unusual feature of Hoover Dam's construction? The dam was built in blocks or vertical columns varying in size from about 60 feet square at the upstream face of the dam to about 25 feet square at the downstream face.

Adjacent columns were locked together by a system of vertical keys on the radial joints and horizontal keys on the circumferential joints. Concrete placement in any one block was limited to 5 feet in 72 hours. After the concrete was cooled, a cement and water mixture called grout was forced into the spaces created between the columns by the contraction of the cooled concrete to form a monolithic (one piece) structure. What were the principal items of work? More than 5,500,000 cubic yards of material were excavated, and another 1,000,000 cubic yards of earth and rockfill placed. By feature, this included: Excavation for the diversion tunnels, 1,500,000 cubic yards; for the foundation of the dam, powerplant, and cofferdams 1,760,000 cubic yards; for the spillways and inclined tunnels, 750,000 cubic yards; for the valve houses and intake towers, 410,000 cubic yards; earth and rockfill for the cofferdams, 1,000,000 cubic yards.

In addition, 410,000 linear feet of grout and drainage holes were drilled, and 422,000 cubic feet of grout were placed under pressure. What were the quantities of principal materials used in the dam? The principal materials, all of which were purchased by the government, were: reinforcement steel, 45,000,000 pounds; gates and valves, 21,670,000 pounds; plate steel and outlet pipes, 88,000,000 pounds; pipe and fittings, 6,700,000 pounds or 840 miles; structural steel, 18,000,000 pounds; miscellaneous metal work, 5,300,000 pounds. What construction work was necessary before operations started at the damsite?

(1) Construction of Boulder City to house both Government and contractor employees; (2) construction of 7 miles of 22-foot wide, asphalt-surfaced highway from Boulder City to the damsite; (3) construction of 22.7 miles of standard-gauge railroad from the Union Pacific main line in Las Vegas to Boulder City and an additional 10 miles from Boulder City to the damsite; and (4) construction of a 222-mile-long power transmission line from San Bernardino, California, to the damsite to supply energy for construction. Lake Mead What is the lake's elevation at high-water? The high-water line is at 1,229 feet above sea level. At this elevation, the water would be more than 7 feet over the top of the raised spillway gates, which are at elevation 1221.4 feet. All lands below elevation 1,250 have been retained for reservoir purposes. How much water will Lake Mead hold? At elevation 1221.4, it would contain 28,945,000 acre-feet.

An acre-foot is the amount of water required to cover 1 acre to a depth of 1 foot, or approximately 326,000 gallons. The reservoir will store the entire average flow of the river for 2 years. That is enough water to cover the State of Pennsylvania to a depth of one foot. How is the reservoir capacity allotted? Below elevation 1,229, about 1,500,000 acre-feet of storage capacity is reserved exclusively for flood control; about 2,547,000 acre-feet for sedimentation control; about 18,438,000 acre-feet for joint use (flood control, municipal and industrial water supply, irrigation, and power); and 7,683,000 acre-feet for inactive storage. Between 1935 and 1963, about 91,500 acre-feet of sediment was deposited in Lake Mead each year. With closure of Glen Canyon Dam, about 370 miles upstream, the life of Lake Mead is indefinite.

Tunnels, Towers, Penstocks and Spillways How was the river diverted during dam construction? The river was diverted around the damsite through four 50-foot diameter tunnels, two on each side of the river drilled through the canyon walls. The tunnels, with a total length of 15,946 feet, or about 3 miles, were excavated to 56 feet and lined with 3 feet (300,000 cubic yards) of concrete. The tunnels could carry over 200,000 cubic feet - more than 1.5 million gallons - of water per second! The river was diverted through the two Arizona tunnels on November 14, 1932. After being used for river diversion, how were the tunnels used? The inner tunnels were plugged with concrete approximately one-third their length below the inlets, and the outer tunnels were plugged approximately halfway. The two inner tunnels contain 30-foot diameter steel pipes which connect the intake towers in the reservoir with the penstocks to the powerplant and the canyon wall outlet works. The downstream halves of the two outer tunnels are used for spillway outlets. What gates are installed on the tunnels?

The inlets of the two outer tunnels are permanently closed with 50- by 50-foot bulkhead gates. Each gate, with steel frame, weighs about 3,000,000 pounds, and required 42 railroad cars for shipment. At the outlets of the two inner tunnels, 50- by 35-foot Stoney gates are installed. These gates can be closed when the tunnels need to be emptied for inspections or repairs. What are the intake towers? They are four reinforced-concrete structures located above the dam, two on each side of the canyon. The diameter of these towers is 82 feet at the base, 63 feet 3 inches at the top, and 29 feet 8 inches inside. Each tower is 395 feet high and each controls one-fourth the supply of water for the powerplant turbines. The four towers contain 93,674 cubic yards of concrete and 15,299,604 pounds of steel. What are the main characteristics of the penstock and outlet pipes?

Forty-four thousand tons of steel were formed and welded into 14,800 feet of pipe varying from 8 to 30 feet in diameter. Each length of the largest pipe - 12 feet long, 30 feet in diameter, and 2 inches thick - was made from 3 steel plates, of such weight that only two plates could be shipped from the steel mill to the fabricating plant on one railroad car. Two such lengths of pipe welded together make one section weighing approximately 135 tons or, at intersections with the penstocks, as much as 186 tons. What outlets are used? Four 72-inch needle valves in each inner diversion tunnel plug outlet; and two 84-inch needle valves each in the Arizona and Nevada canyon wall valve houses. The needle valves in the canyon walls are about 180 feet above the river. These valves are designed to bypass water around the dam under emergency or flood conditions, or to empty the penstocks for maintenance work. What is the maximum capacity of these works?

About 118,000 cubic feet per second: 32,000 cubic feet per second for power generation and 86,000 cubic feet per second of valve discharge. One cubic foot per second of water equals nearly 7 gallons passing a given point in one second. What are the Arizona and Nevada spillways? Concrete-lined open channels about 650 feet long, 150 feet wide, and 170 feet deep on each canyon wall. More than 600,000 cubic yards of rock were excavated for the spillways. The spillway walls are lined with 18 inches of concrete and the floors with 24 inches; 127,000 cubic yards of concrete were placed for the spillways. How is water discharged from the spillways? Into the outer diversion tunnels through inclined shafts 50 feet in diameter and 600 feet long. The discharge is controlled by four automatically or manually operated 100- by 16-foot, 500,000-pound drum gates on each spillway crest.

Maximum water velocity in the spillway tunnels is about 175 feet per second, or 120 miles per hour. What is the maximum discharge capacity of the spillways, valves, and powerplant? Five hundred and eighteen thousand ft3/s. Each spillway can discharge 200,000 ft3/s. If the spillways were operated at full capacity, the energy of the falling water would be about 25,000,000 horsepower. The flow over each spillway would be about the same as the flow over Niagara Falls, and the drop from the top of the raised spillway gates to river level would be approximately three times as great. Power Development Where is the powerplant located? In a U-shape structure at the base of the dam. Each powerplant wing is 650 feet long, 150 feet above normal tailrace water surface, and 299 feet (nearly 20 stories) above the powerplant foundation. In all of the galleries of the plant there are 10 acres of floor space. What is the capacity of the Hoover Powerplant? There are 17 main turbines in Hoover Powerplant.

The original turbines were all replaced through an uprating program between 1986 and 1993. With a rated capacity of 2,991,000 horsepower, and two station-service units rated at 3,500 horsepower each, for a plant total of 2,998,000 horsepower, the plant has a nameplate capacity of 2,074,000 kilowatts. This includes the two station-service units, which are rated at 2,400 kilowatts each. When were the power installations in the plant completed, and of what do they consist? Installation was completed in 1961. With the uprating completed in 1993, there are fifteen 187,000 horsepower, one 100,000 horsepower, and one 86,000 horsepower Francis-type vertical hydraulic turbines. There are thirteen 130,000 kilowatt, two 127,000 kilowatt, one 61,500 kilowatt, and one 68,500 kilowatt generators.

All machines are operated at 60 cycles. There are also two 2,400 kilowatt station-service units driven by Pelton water wheels. These provide electrical energy for lights and for operating cranes, pumps, motors, compressors, and other electrical equipment within the dam and powerplant. Who are the principal contractors for energy? The States of Arizona and Nevada; the City of Los Angeles; the Southern California Edison Co.; the Metropolitan Water District of Southern California; the California cities of Glendale, Burbank, Pasadena, Riverside, Azusa, Anaheim, Banning, Colton, and Vernon; and the city of Boulder City, Nevada. How is the firm energy generated at Hoover Dam allocated? Arizona - 18.9527 percent; Nevada - 23.3706; Metropolitan Water District of Southern California - 28.5393 percent; Burbank - 0.5876 percent; Glendale -1.5874 percent; Pasadena - 1.3629 percent; Los Angeles - 15.4229 percent; Southern California Edison Co.

- 5.5377 percent; Azusa - .1104 percent; Anaheim - 1.1487 percent; Banning - 0.0442 percent; Colton - 0.0884 percent; Riverside - 0.8615 percent; Vernon - 0.6185 percent; and Boulder City, Nevada - 1.7672 percent. How is the income from the sale of energy used? To pay all operation and maintenance expenses and to repay the major part of the construction cost of the dam and powerplant, at interest not exceeding 3 percent. The cost of construction completed and in service by 1937 was repaid on May 31, 1987. All other costs, except those for flood control, will be repaid within 50 years of the date of installation or as established by Congress. Repayment of the $25 million construction cost allocated to flood control is currently deferred. In addition, Arizona and Nevada each receive $300,000 annually in lieu of taxes.

Hoover Dam Sculptures One of the highlights for many of the people who visit Hoover Dam each year is the sculpture work they find. While most people are impressed by these works, they often ask the question, "What do they mean?" Much of the sculpture is the work of Norwegian-born, naturalized American Oskar J.W. Hansen. Mr. Hansen fielded many questions about his work while it was being installed at the dam. In response to those questions, he later wrote about his interpretation of his sculptures. Hoover Dam, said Hansen, represented for him the building genius of America, "a monument to collective genius exerting itself in community efforts around a common need or ideal." He compared the dam to such works as the great pyramids of Egypt, and said that, when viewing these man-made structures, the viewer often asks of their builders, "What manner of men were these?" The sculptor, according to Hansen, tries to answer this question objectively, by "interpreting man to other men in the terms of the man himself." In each of these monuments, he said, can be read the characteristics of these men, and on a larger scale, the community of which they are part.

Thus, mankind itself is the subject of the sculptures at Hoover Dam. Hansen's principal work at Hoover Dam is the monument of dedication on the Nevada side of the dam. Here, rising from a black, polished base, is a 142-foot flagpole flanked by two winged figures, which Hansen calls the Winged Figures of the Republic. They express "the immutable calm of intellectual resolution, and the enormous power of trained physical strength, equally enthroned in placid triumph of scientific accomplishment." "The building of Hoover Dam belongs to the sagas of the daring. The winged bronzes which guard the flag therefore wear the look of eagles. To them also was given the vital upward thrust of an aspirational gesture; to symbolize the readiness for defense of our institutions and keeping of our spiritual eagles ever ready to be on the wing." The winged figures are 30 feet high. Their shells are 5/8-inch thick, and contain more than 4 tons of statuary bronze. The figures were formed from sand molds weighing 492 tons. The bronze that forms the shells was heated to 2,500 degrees Fahrenheit, and poured into the molds in one continuous, molten stream.

The figures rest on a base of black diorite, an igneous rock. In order to place the blocks without marring their highly polished finish, they were centered on blocks of ice, and guided precisely into place as the ice melted. After the blocks were in place, the flagpole was dropped through a hole in the center block into a predrilled hole in the mountain. Surrounding the base is a terrazzo floor, inlaid with a star chart, or celestial map. The chart preserves for future generations the date on which President Franklin D. Roosevelt dedicated Hoover Dam September 30, 1935. The apparent magnitudes of stars on the chart are shown as they would appear to the naked eye at a distance of about 190 trillion miles from earth. In reality, the distance to most of the stars is more than 950 trillion miles. In this celestial map, the bodies of the solar system are placed so exactly that those versed in astronomy could calculate the precession (progressively earlier occurrence) of the Pole Star for approximately the next 14,000 years.

Conversely, future generations could look upon this monument and determine, if no other means were available, the exact date on which Hoover Dam was completed. Near the figures and elevated above the floor is a compass, framed by the signs of the zodiac. Hansen also designed the plaque commemorating the 96 men who died during the construction of Hoover Dam, as well as the bas-relief series on both the Nevada and Arizona elevator towers. The plaque, originally set into the canyon wall on the Arizona side of the dam, is now located near the winged figures. It reads: "They died to make the desert bloom. The United States of America will continue to remember that many who toiled here found their final rest while engaged in the building of this dam. The United States of America will continue to remember the services of all who labored to clothe with substance the plans of those who first visioned the building of this dam." The five bas-reliefs on the Nevada elevator tower, done in concrete, show the multipurpose benefits of Hoover Dam flood control, navigation, irrigation, water storage, and power.

On the Arizona elevator tower is a series of five bas-reliefs, also in concrete, depicting "the visages of those Indian tribes who have inhabited mountains and plains from ages distant." Accompanying the illustrations is the inscription, "Since primordial times, American Indian tribes and Nations lifted their hands to the Great Spirit from these ranges and plains. We now with them in peace buildeth again a Nation." Lake Mead | Lake Mead National Recreation Area Contact Us Lake Mead National Recreation Area Lake Mead was formed by the impounding of the Colorado River by the Hoover Dam. The lake is the largest reservoir in the United States. It extends for 110 miles behind the dam, forming the border part of the way between the states of Nevada and Arizona. The south end of the lake is located about 30 miles east of Las Vegas. It is about 247 square miles in size. The lake offers year round recreation activities for nearby residents and visitors from all over. Activities include boating, swimming, fishing, water skiing, kayaking, and sun bathing. The lake has about 550 miles of shoreline with many coves with sandy beaches and rocky cliffs to explore.

Houseboat rentals are popular in the summertime on the lake. High temperatures on the lake in the summer are routinely in excess of 100 degrees. Lake Mead is named after Elwood Mead, who was the commissioner of the U.S. Bureau of Reclamation during the planning and construction fo the Hoover Dam project. After the completion of the Hoover Dam in 1936, the dam caused the water level to rise, forming Lake Mead. The area was originally called the Boulder Dam Recreation Area, until it was renamed Lake Mead National Recreation Area in 1964. There are no cities on Lake Mead's edge, but more than two million people that live within 40 miles of the lake. When the Hoover Dam was built, the city of St. Peters was submerged by Lake Mead as the dam caused the Colorado River's water level upriver from the dam to rise. The U.S. federal government purchased the town. The ruins of St. Thomas are now protected by the National Park Service as a historic site. The ruins are sometimes visible when the water level on Lake Mead is low.

The cities nearest Lake Mead are Boulder City , Nevada on the south end near the Hoover Dam and Moapa Town, Nevada near the north end. Boulder City is a larger city of about 15,000 residents, eight miles west of the Hoover Dam. It offers hotels, restaurants, shopping, golf, and hiking trails for visitors. Lake Mead's water level has dropped significantly in the past decade. This is evident to visitors as prior water levels can be observed on the rocks around the lake. Continued low levels at the lake could cause significant water shortages in the Las Vegas area. Already, several marinas and boat ramps have had to have been relocated or closed as a result of the low water levels. The demands for water have never been greater as the Las Vegas areas population has grown by more than 25% in the past decade. This combined with less snowmelt and precipitation upriver cause serious concerns over the area's available water supply. Hoover Dam | The Dam That Created Lake Mead Hoover Dam A Treasure of Arizona, Nevada & The World Construction began in 1931 and Hoover Dam was completed in 1936.

It still stands tall as an engineering marvel high above the Colorado River between Arizona and Nevada. Hoover Dam attracts over 7 million visitors from around the new world every year feeding vast tourism into the Las Vegas Nevada and Arizona economy. The building of Hoover Dam took the brilliance of over 200 engineers to pull-off what many deemed as almost impossible. And it was the fortitude of over 7,000 dam workers that endured amazingly harsh conditions and extreme dangers to complete Hoover Dam almost two years ahead of schedule. Read more about “Men, Women and Children of Hoover Dam” . The mission of Hoover Dam was multi-purpose. Flooding along the Colorado River as it made its way to the Gulf of California had to be controlled. The water-flow had to be harnessed to provide much needed water to the fertile, yet arid agricultural areas of California and Arizona. And hydroelectric energy was to satisfy the requirements of millions and millions of people in adjacent regions. A scenic by-product of Hoover Dam is the gigantic reservoir of Lake Mead, a stunningly beautiful water recreation wonderland. This boating, sailing, fishing and house-boating paradise attracts over 10 million visitors a year.

Lake Mead covers 550 miles of majestic shoreline and 247 square miles of area which is twice the size of Rhode Island. Its capacity of 1 1/4 trillion cubic feet of water would cover the entire state of Pennsylvania one foot deep. But, back to Hoover Dam itself which is 726 feet tall and 1,244 feet long. At its base, Hoover Dam is 660 feet thick which is 60 feet longer than two football fields laid end-to-end. Combined with its top thickness of 45 feet, there is enough concrete (4.5 million cubic yards) in Hoover Dam to build a two-lane highway from Seattle Washington to Miami Florida. Or imagine a four-foot wide sidewalk around Earth at its equator. An often asked question is how Hoover Dam can withstand the massive pressure and weight of Lake Mead which is constantly trying to flow down river to the Gulf of California. It’s answered briefly this way. Hoover Dam curves against Lake Mead and is fortified against the massive rock walls of Black Canyon. When the water compresses against the curved walls of Hoover Dam, the canyon walls push-back counteracting the awesome power of Lake Mead.

This massive, but unseen, action squeezes the concrete arch together creating the mind-boggling strength of Hoover Dam. Read more about the construction of Hoover Dam . Hoover Dam is only about 35 miles from Las Vegas Nevada making it a popular tourist destination of those visiting the casinos and nightlife that never sleeps. Over 20,000 vehicles a day cross Hoover Dam between Arizona and Nevada. Thousands from around the world take the Hoover Dam tour and ride the elevator down into the inner-workings of the dam. Hoover Dam offers ample parking in strategically located scenic areas overlooking the spectacular views across Hoover Dam to Lake Mead and the Colorado River through Black Canyon. Food, refreshments and tour guides make the visit even more enjoyable. There is an abundance of fine hotels, budget motels and nearby casino hotels and resorts. Boat rentals and houseboat rentals area available at Lake Mead marinas and helicopter tours are an excellent way to experience the beauty of the entire area. And, be on the lookout for the rare Mountain Sheep that inhabit the mountainous canyons. Visit Hoover Dam. You’ll be amazed.

Hoover Dam - Lake Mead - Hoover Dam Bridge - Boulder Dam - DesertUSA Hoover Dam Visitor Information - Security - Traffic Information With the official opening of the Hoover Dam Bypass Bridge (Mike O'Callaghan – Pat Tillman Memorial Bridge) in October 2010, vehicles travelling on U.S. Highway 93 no longer cross Hoover Dam. Visitors to the dam must now exit US 93 at Nevada State Route 172 to reach the dam. Additionally, State Route 172 is not open to through-traffic, as the roadway on the Arizona side of the site has been closed. Vehicles can still cross the dam to visit the Arizona viewpoints and concessions, but all are required to turn around and re-enter Nevada to access Highway 93. Visitors can park in designated lots and walk across the dam for better viewing and photographic opportunities, during daylight hours only. At no time will any vehicles be allowed to stop on top of the dam. Pedestrians are prohibited from the top of the dam during hours of darkness. View from the Hoover Dam Bypass Bridge Overview of Hoover Dam Originally called Boulder Dam, this engineering marvel was renamed for Herbert Hoover, the 31st president of the United States.

As a conservationist, he was a strong proponent of preserving our natural resources and protecting the nation's lands from misuse, and from destruction by disastrous floods. As an engineer, he strongly supported construction of a high concrete dam on the Colorado River to control the river, and to provide irrigation water to the rich farmlands nearby, and a dependable supply of water for Southern California communities. President Hoover advocated that the Boulder Canyon Project be self-supporting, financed entirely through the sale of hydroelectric power generated at the dam. He was personally involved in the pre-construction discussions concerning the location, feasibility and safety of the dam -- a dam of unprecedented height and weight and the key to control and regulation of the Colorado River. Lodging Hotels/Motels There are hotels and motels in Boulder City , Henderson , Laughlin , Bullhead City and Las Vegas. See map to right for locations of cities. Click on the name of the city above for rates, availability and reservation online. The Hoover Dam Visitor Center is open, and you are encouraged to visit the facility. The new Discovery Tour is a self-paced tour which provides live presentations at six different locations at the top of the dam. For more information about the new Discovery Tour click here.

Noncommercial vehicles that may cross the dam include: Passenger cars History Construction of Hoover Dam began in 1931, and the last concrete was poured in 1935, two years ahead of schedule. President Franklin D. Roosevelt dedicated the dam on September 30, 1935. The power plant structures were completed in 1936, and the first generator began commercial operation in October of that year. The 17th and final generator went into commercial operation in 1961. Hoover Dam was without precedent; it was the greatest dam constructed in its day. An arch-gravity structure rising 726 feet above bedrock, Hoover is still the Western Hemisphere's highest concrete dam. It is 660 feet thick at its base, 45 feet thick at its crest, and stretches 1,244 feet across Black Canyon. There are 4.4 million cubic yards of concrete in the dam, power plant and related structures. Hoover Dam pioneered the Bureau of Reclamation's efforts in multiple-purpose water resources development. The dam controls floods while it stores water for irrigation, municipal, and industrial uses.

The dam also provides hydroelectric power generation, recreation and fish and wildlife habitat. Dam Benefits Colorado River water irrigates more than a million acres of land in the U.S., and nearly half a million acres in Mexico. The water helps meet the municipal and industrial needs of over 14 million people. As it passes through Hoover's turbines, the water generates low-cost hydroelectric power for use in Nevada, Arizona and California. About 4 billion kilowatt-hours of energy, enough for 500,000 homes, are generated annually. Irrigation & Storage Water that was once muddy is now sparkling clear in reservoirs and in stretches of the Colorado River. Hoover and other dams on the Colorado have tamed the turbulent flow, creating clean bodies of water that provide recreation for more than 10 million people each year. These waters have also provided habitats for fish and wildlife in areas that were once nearly barren. Colorado River water stored behind Hoover Dam irrigates some of America's richest farmlands. Valley and mesa lands in the warm desert climate along the river grow a wide variety of fruits, vegetables and other non-surplus crops throughout the year.

Major irrigation projects which benefit from Hoover's control and regulation of the Colorado River include the Palo Verde Valley, the Colorado River Indian Reservation, the Yuma and Gila projects in Arizona, and the Imperial and Coachella valleys in California. By regulating the Colorado River, Hoover Dam assures a steady flow of municipal and industrial water to Los Angeles, San Diego and other cities in the Southwest. Phoenix, Arizona was added to the list when the Central Arizona Project began delivering water in 1985. The Tucson area began to receive project water in 1991. Several agriculture users, a number of smaller cities, and an Indian community between Phoenix and Tucson also benefit from the availability of water. Part of the hydroelectric energy generated at Hoover and Parker dams helps pump water along the Colorado River Aqueduct. The 242-mile-long aqueduct has an annual capacity of 1.212 million acre-feet (1 billion gallons) of water a day. Five pumping stations lift the water 1,617 feet over the mountains between the Colorado River and the coastal plain. Homes and industries in the Las Vegas metropolitan area receive Colorado River water from Lake Mead through the Robert B.

Griffith Water Project, which was completed in 1982. Hydroelectric Power Hydroelectric power is created as water rushes through turbines that activate generators. When the water has completed its task, it flows on unchanged to serve other needs. The electricity produced is clean, nonpolluting and, unlike many other forms of energy, renewable. Through the sale of power and water, a major portion of the money used to construct Reclamation projects is returned to the Federal Treasury. Hoover Dam's approximate $175 million cost was repaid over a 50-year period, with interest. Hoover Dam and power plant revenues from the sale of water and power have repaid approximately $260 million, including interest, to the Federal Treasury, principally from 50-year power contracts that ended May 31, 1987. Several contingencies, including $25 million allocated to flood control, will be repaid with interest over the 30-year contract period which began June 1, 1987. Water is released from Lake Mead through similar sets of diversion works in both walls of Black Canyon.

The water, drawn through the intake towers, flows through pipes called penstocks, to the power plants. The penstocks can also be used to discharge water directly from the reservoir to the river below the dam. The spillways were tested in 1941 and not used again until the record high flows of 1983. Vital Statistics Height: 726.4 feet (221.28 meters) Crest Length: 1,244 feet (379.2 meters) Top Thickness: 45 feet (13.7 meters) Bottom Thickness: 660 feet (201.2 meters) Composition: 3.25 million cubic yards (2.5 million cubic meters) of concrete. The Reservoir (Lake Mead) Lake Mead and Hoover Dam Lake Mead and Hoover Dam From our starting point in Las Vegas, it's about 30 miles to Lake Mead National Recreation Area. The lake was formed by the waters of the Colorado River which are held back by Hoover Dam. It sits on the border between Arizona and Nevada.

Due to recent drought conditions, the water in Lake Mead is pretty low, but it's still open for recreational boating and bathing. Below, Jesse and Matthew stand on the edge of a hill, with Lake Mead as the backdrop. A few miles down the road from that spot, we meet up with U.S. 93, which crosses the top of Hoover Dam. There is a multilevel parking garage and visitor's center on the Nevada side of the dam. Aside from creating Lake Mead, Hoover Dam is a hydroelectric power plant, generating power for Arizona, Nevada and California. The inclined electrical tower in the photo above & below is carrying some of the power out from the transformers below, in Black Canyon. I've highlighted a large circular thermometer on the side of the visitor's center. It reads 115 degrees.....but it's a DRY heat. HAH! Also in the photos below you can see cables going across the canyon. The cables which span the canyon are part of a construction cableway crane system. A major highway project is underway, which when completed in 2008, will reroute the U.S.

93 traffic over a new 2000 foot bridge, just south of the dam. The pylons on the Nevada side of the canyon, as well as the concrete support columns for the bridge can be seen top left and center in the picture above. The 2 structures in the center of the photo which seem to rise up out of the canyon comprise the recently built visitor's center. Above are the 8 main turbines on the Nevada side of the complex, deep within Black Canyon. On our visit, only 7 of the 8 are running, as indicated by the light on top of each generating unit. There are 9 more on the Arizona side. Water from Lake Mead enters through 4 intake towers, 2 on the Arizona side, 2 on the Nevada side. The one below is on the NV side, and you can see by the stains on the surrounding rocks, the water level is very low. Water would never run over the top of the dam. If the level of Lake Mead ever exceeded normal levels, there are spillways on each side of the dam, which are 27 feet below the top of the dam.

There'd have to be a 100 foot rise from today's levels in order for water to crest over the spillway. Below, one of these spillways, and the 50 foot diameter tunnel built to take the water through the canyon and out below the dam. Back on top of the dam, here's a look down at the powerhouse and canyon over 700 feet below. Time to recharge the batteries? Here I am grabbing an insulator, like the ones on the steel electrical tranmission towers here. For more information on Hoover Dam, visit the Dept. of the Interior's Official Site . For more about the Hoover Dam Bypass project, which will put a new bridge over the Colorado River just 1500 feet downstream of Hoover Dam, visit . Click to go to the next page, Bryce National Park . All content ï¿½2006 Jeff Baker.us All Rights Reserved. Hoover Dam - Facts & Summary - HISTORY.com Google At the turn of the 20th century, farmers sought to divert the Colorado River to budding Southwestern communities via a series of canals.

When the Colorado broke through the canals in 1905, creating the inland Salton Sea, the job of controlling the raging river fell to the U.S. Bureau of Reclamation. Bureau director Arthur Powell Davis in 1922 outlined a plan before Congress for a multipurpose dam in Black Canyon, located on the Arizona- Nevada border. Named the Boulder Canyon project, after the original proposed site, the dam would not only control flooding and irrigation, it would generate and sell hydroelectric power to recoup its costs. Still, the proposed $165 price tag concerned some lawmakers, while representatives of six of the seven states in the river drainage area—Colorado, Wyoming , Utah , New Mexico , Arizona and Nevada —worried that the water would primarily go to California . Secretary of Commerce Herbert Hoover brokered the 1922 Colorado River Compact to divide the water proportionally among the seven states, but the legal wrangling continued until outgoing President Calvin Coolidge authorized the Boulder Canyon Project in December 1928. In honor of the new president’s contributions, Secretary of the Interior Ray L.

Wilbur announced the structure would be called Hoover Dam at a 1930 dedication ceremony, though the name didn’t become official until 1947. As the Great Depression unfolded, hopeful laborers descended on Las Vegas and set up camp in the surrounding desert for the chance to work on the project. Those who were hired eventually moved to Boulder City, a community specifically built six miles from the work site to house its employees. Meanwhile, the U.S. government set about finding a contractor to build the proposed 60-story arch dam. The contract was awarded in March 1931 to Six Companies, a group of construction firms that had pooled its resources to meet the steep $5 million performance bond. The first difficult step of construction involved blasting the canyon walls to create four diversion tunnels for the water. Facing strict time deadlines, workers toiled in 140-degree tunnels choked with carbon monoxide and dust, conditions that prompted a six-day strike in August 1931. When two of the tunnels were complete, the excavated rock was used to form a temporary coffer dam that successfully rechanneled the river’s path in November 1932.

The second step of involved the clearing of the walls that would contain the dam. Suspended from heights of up to 800 feet above the canyon floor, high scalers wielded 44-pound jackhammers and metal poles to knock loose material, a treacherous task that resulted in casualties from falling workers, equipment and rocks. Meanwhile, the dried riverbed allowed for construction to begin on the powerplant, four intake towers and the dam itself. Cement was mixed onsite and hoisted across the canyon on one of five 20-ton cableways, a fresh bucket capable of reaching the crews below every 78 seconds. Offsetting the heat generated by cooling concrete, nearly 600 miles of pipe loops were embedded to circulate water through the poured blocks, with workers continually spraying the concrete to keep it moist. As the dam rose, block by block, from the canyon floor, the visual renderings of architect Gordon Kaufmann took form. Electing to emphasize the imposing mass of the structure, Kaufmann kept the smooth, curved face free of adornment. The powerplant was given a futuristic touch with horizontal aluminum fins for windows, while its interior was designed to pay homage to Native American cultures.

With the body of water that would become Lake Mead already beginning to swell behind the dam, the final block of concrete was poured and topped off at 726 feet above the canyon floor in 1935. On September 30, a crowd of 20,000 people watched President Franklin Roosevelt commemorate the magnificent structure’s completion. Approximately 5 million barrels of cement and 45 million pounds of reinforcement steel had gone into what was then the tallest dam in the world, its 6.6 million tons of concrete enough to pave a road from San Francisco to New York City. Altogether, some 21,000 workers contributed to its construction. Hoover Dam fulfilled the goal of disseminating the one-wild Colorado River through the parched Southwest landscape, fueling the development of such major cities as Los Angeles, Las Vegas and Phoenix. Capable of irrigating 2 million acres, its 17 turbines generate enough electricity to power 1.3 million homes. The dam was designated a National Historic Landmark in 1985 and one of America’s Seven Modern Civil Engineering Wonders in 1994.

It receives some 7 million visitors annually, while Lake Mead, the world’s largest reservoir, hosts another 10 million as a popular recreation area. Tags NCHGC: Sites and Stories: Adjacent Lands: Lake Mead sites | south rim | north rim | rim viewpoints | rim to river & trails | colorado river corridor | beyond park boundaries Though Grand Canyon National Park contains one of the seven wonders of the natural world, crafted over millions of years of erosion and other natural forces, it is capped on either end by huge artificial landscapes that took humans less than two decades to create. Here Black Canyon is shown in 1922 before construction of Hoover Dam; compare this with the picture below. Photo: Bureau of Reclamation (Click on photos to enlarge) At the southwestern edge of Grand Canyon National Park, on the Arizona-Nevada line, the Colorado River flows into Lake Mead, one of the largest manmade lakes in North America. It began filling upon the completion of Hoover Dam (previously known as Boulder Dam) in 1935. The largest hydroelectric dam in the world at the time of its construction, Hoover Dam was completed in less than five years.

It stretches across the Colorado River at Black Canyon, about 30 miles east of Las Vegas. Today Hoover Dam is a National Historic Landmark, and remains the highest concrete arch dam in the United States. The lake that formed behind it is named for Elwood Mead, the head of the Bureau of Reclamation from 1924-1936, who left a major imprint on the water policy and landscape of the West. Before the dam was constructed, outsiders rarely visited this area because of its extreme temperatures, harsh landscapes, and lack of roads. Still, it was a landscape with significant natural and cultural resources. The first inhabitants of the area lived between 8,000 and 10,000 years ago, when the environment was wetter and cooler. Over the centuries many different Native American cultures made their homes in the area, some hunting and gathering, others farming. In the 19th century, Euro-American explorers such as Jedediah Smith, Joseph Christmas Ives, and John Wesley Powell traveled through the area. Once Hoover Dam was completed and the lake filled, however, thousands of tourists suddenly flocked to enjoy the refreshing waters and bask in the steady sun.

The Bureau of Reclamation, which built the dam, knew that the lake it created could be turned into a major recreation site, but its focus was on developing water storage projects. Therefore, the Bureau joined forces with the National Park Service, which had experience in recreation management, to develop the area. Hoover Dam (center left) was built across Black Canyon, backing up the Colorado River 25 miles to the southwestern end of Grand Canyon National Park. The resulting Lake Mead offers water recreation activities to visitors at Lake Mead National Recreation Area. Photo: National Park Service Steep rock slopes, formerly the walls of canyons, today contain the deep blue waters of Lake Mead, which led to the creation of the first national recreation area in the United States. Photo: NPS In 1936, these two agencies cooperatively created the Boulder Dam Recreation Area, the first national recreation area established in the United States. It included the Hoover Dam itself as well as 25 miles of the Colorado River. Eleven years later, the agencies changed the name to Lake Mead National Recreation Area. In 1950 Davis Dam was completed near Bullhead City, Arizona.

This dam and the lake it created, Lake Mohave, were incorporated into Lake Mead National Recreation Area as well. In 1963 President John F. Kennedy initiated the policy that Congress must establish all future National Recreation Areas (NRAs), and the next year Lake Mead National Recreation Area became the first such area established by Congressional statute. Today, out of 43 NRAs, the Park Service administers 20, most of which are centered on large reservoirs that emphasize water-based recreation. Other agencies, including the Forest Service and Bureau of Land Management, administer the 23 other NRAs. Lake Mead NRA contains 1.5 million acres, making it twice the size of Rhode Island. It has about 550 miles of shoreline, though the area covered by water comprises less than 13 percent of the total area of the NRA. It also includes nine designated wilderness areas, as shown in the NPS diagram at right. Part of the NRA overlaps with portions of Grand Canyon-Parashant National Monument, created in 2001, on the Arizona Strip .

Although most of the eight million visitors it attracts every year see it purely as a recreation spot, the lake is actually a giant reservoir, storing water that is delivered to farms, homes, and businesses in Nevada, Arizona, California, and Mexico. The Mojave, Great Basin, and Sonoran Deserts, three of the four American desert ecosystems, all intersect at Lake Mead Recreation Area. Elevations within Lake Mead NRA range from about 500 feet to nearly 7000 feet above sea level. Temperatures in the summer can easily reach over 110 degrees, though winters are mild. Even though the land is arid and hot, it is home to a surprising array of birds, mammals, fish, and reptiles. These include bighorn sheep, kit fox, ringtail cats, desert tortoise, chuckwalla lizards, Gila monsters, and several kinds of rattlesnakes. Though the cacti and creosote that dot the landscape may make it seem barren, in the springtime it comes alive as rain showers spur the growth of colorful wildflowers. The history of Lake Mead NRA intersects with that of Grand Canyon National Park just as its ecosystem does.

For instance, in 1953 Lake Mead NRA was the site of the first concessionaire-operated trailer park within the National Park System. The NPS in the 1950s was looking for a way to serve the growing number of tourists coming to visit sites within the national park system, and kept an eye on this site to see whether a similar system could be implemented in other parks. The experiment was successful, and in 1961 Grand Canyon National Park became the first park to open this type of facility. Lake Mead NRA is Lake Mead's Water Sinks to Lowest Level Since 1930s Lake Mead's Water Sinks to Lowest Level Since 1930s By Elizabeth Goldbaum, Staff Writer | August 20, 2015 09:13am ET MORE Satellite photo of Lake Mead captured July 24, 2015 by the Operational Land Imager (OLI) on the Landsat 8 satellite. Credit: Joshua Stevens Years of unrelenting drought are straining a large reservoir of water between Nevada and Arizona, new satellite images reveal.

Images taken July 25 show that Lake Mead’s water level has dropped by about 120 feet (37 meters) from where the water reached 15 years ago, on July 6, 2000. The Landsat 8 satellite, jointly managed by NASA and the U.S. Geological Survey, captured both photos of the sprawling reservoir. Lake Mead is no stranger to droughts . The man-made lake hit lower-than-average water levels in the mid-1950s and mid-1960s, and the current depletion is part of a decade-long trend, according to NASA. Lake Mead's current low level hasn't been recorded since the 1930s, when the lake was first being filled, agency officials said. [ Dry and Dying: Images of Drought ] Satellite photo of Lake Mead captured July 6, 2000 by the Operational Land Imager (OLI) on the Landsat 8 satellite. Credit: Joshua Stevens Lake Mead formed as a byproduct following construction of the Hoover Dam, which was built between 1931 and 1936.

The Hoover Dam is a concrete structure that was developed to harness the Colorado River, author Joseph Stevens wrote in his book " Hoover Dam: An American Adventure " (University of Oklahoma Press, 1988). The iconic white concrete wedge that straddles the border between Arizona and Nevada created a huge reservoir that was named Lake Mead after Elwood Mead, a commissioner of the Bureau of Reclamation, who died of a heart attack in January 1936, according to Stevens. The reservoir can hold 9.3 trillion gallons (36 trillion liters) of water at maximum capacity. Most of the water trickles down from surrounding mountains as snowmelt, enters Lake Powell, travels through the Grand Canyon and eventually makes its way to Lake Mead, according to NASA. Arizona, Nevada, California and northern Mexico all depend on Lake Mead's water, with the Las Vegas Valley relying on the reservoir for about 90 percent of its water supply, NASA officials said. Lake Mead’s northern branch, called Overton Arm, is noticeably narrower in the 2015 satellite image. Overton Arm stops short of the confluence of the west-lying Muddy River and the east-lying Virgin River.

The Virgin River Basin, which is the circular feature that once attached to Overton Arm, looks parched in the new photo. The shorelines of Boulder Basin to the west and Gregg Basin to the east also look different compared to their water levels in the satellite view from July 2000, according to NASA. Simultaneously, populations are settling farther into the desert, continuing a trend that was noticed in previous images from space that span a 25-year period, beginning in 1984, NASA officials said. In 2008, a study concluded that Lake Mead could dry up by 2021 . In 2010, the reservoir reached its lowest level since 1956.

Question: Which lake was formed by the construction of the Hoover Dam on the Colorado river?
Answer: LAKE MEAD